Santa Monica Bay Research on Oxygen Minimum

This summer our group successfully finished field work in the Santa Monica Basin to study the potential spreading of the Oxygen Minimum Zone (OMZ). The research is funded through a USC Sea Grant project (PIs: Will Berelsen, USC and Tina Treude, UCLA) and a UCLA Faculty Research Grand. We studied the water column and sampled sediments for biogeochemical analyzes along a transect from 70 to 900 m water depth using a CTD and a multicorer on board the R/V YELLOWFIN (Southern California Marine Institute). Students from a UCLA Fiat Lux course (teacher: Tina Treude) and from the Mt. San Antonio College (teacher: Tania Anders) joined some of the trips to become engaged in ocean research.

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PhD students graduated

Congratulations to my PhD students Jessica Gier and Sonakshi Mishra, who both successfully defended their PhD thesis at GEOMAR, University of Kiel (Germany) last week. As well as belated congrats to Johanna Maltby, who defended her thesis in October 2015.

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Seabed as a long-term deposit for plastic

Kiel marine scientists investigate the depletion of plastic bags in the sediment

10 February 2016/Kiel. Marine scientists from Kiel have examined whether and how quickly bacteria deplete plastic bags in the sediment of the seabed. The study shows that classic carrier bags made of polyethylene and biodegradable plastic bags didn’t change at all after hundred days in the seafloor. The results were recently published in the international journal Marine Pollution Bulletin.

Whether on the coasts of the Antarctic or on the sediments of the deep sea – there is barely a place on Earth without plastic waste. But how long plastic will remain in the seas until it is decomposed, is hardly investigated. A group of scientists of the GEOMAR Helmholtz Centre for Ocean Research Kiel, the Kiel University and the Cluster of Excellence “The Future Ocean” now have compared the changes of standard polyethylene carrier bags with those of so-called biodegradable plastic bags in two chemical environments, which are typical for the seabed. As the team in the international journal Marine Pollution Bulletin writes, bacteria have colonized the biodegradable bags significantly faster. However, “there is no reduction or change of material detectable in both kinds of bags within hundred days,” says Alice Nauendorf, first author of the study.

The team used sediment samples from the Eckernförde Bay in the Western Baltic Sea. “In the upper layers of these sediment samples oxygen was still present, but not in the lower layers. That is typical for seafloors around the world”, says the biological oceanographer Nauendorf and adds: “These layers also differ in the types of bacteria who live therein.”

The two bags were placed in both oxic and anoxic sediments for about one hundred days in a laboratory experiment. According to the manufacturer, the biodegradable bag was made of compostbale polyester, cornstarch and undisclosed ingredients.

After the 100 days the team used a number of analytical methods such as high-precision weight measurements, scanning electron microscopy, and Raman spectroscopy to demonstrate possible changes of the material. “We could clearly see that the compostable bags were more populated with bacteria – in the oxygen-containing layers five times more, in the oxygen-free layers even eight times more than the polyethylene bag”, says Nauendorf.

The studies also showed that the material of both bags has not changed at all in the hundred days of the experiment. “We found no weight loss or chemical alteration. Therefore no decomposition of the material is suggested”, emphasizes Prof. Dr. Tina Treude, principal investigator of the study, who now works at the University of California, Los Angeles (UCLA). The exact reason for the different settlement with bacteria remains uncertain. “We found an antibacterial substance in the polyethylene bag, which could have restricted bacterial colonization “, says Nauendorf.

 

But despite the still remaining questions the study shows that plastic reduction is only a very slow process in the sediments. Even the settlement with bacteria is obviously no guarantee for the chemical conversion of a substance. “The study suggests that the seafloor would become a long-term deposit for plastic waste if we don’t stop polluting the seas. Future studies have to show what impact plastic waste has on benthic ecosystems,” says Professor Treude.

Reference:

Nauendorf, A., S. Krause, N. Bigalke, E. V. Gorb, S. N. Gorb, M. Haeckel, M. Wahl, T. Treude (2015): Microbial colonization and degradation of polyethylene and biodegradable plastic bags in temperate fine-grained organic-rich marine sediments. Marine Pollution Bulletin, http://dx.doi.org/10.1016/j.marpolbul.2015.12.024

Link to GEOMAR Website: http://www.geomar.de/en/news/article/meeresboden-als-langzeitdeponie-fuer-plastik/

New Group Member Sydnie Lemieux

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On September 22nd my new group member Sydnie Lemieux started at UCLA. Sydnie is a new Master/PhD student in AOS and will be involved in studying biogeochemical reactions at the sediment-water interface of oxygen minimum zones in the ocean basins off Los Angeles (and beyond) to better understand why these zones are intensifying and what the consequences of this intensification are.

Sydnie recently received her Bachelor of Science in Earth Systems Geoscience at the University of Arizona. While there, she worked as a Research Assistant in Dr. Julia Cole’s Paleoclimate Variability Lab studying past climate behavior using coral cores and cave speleothems. Her independent research project observed sea surface salinity and temperature in the Eastern Pacific, using a 113-year-old coral record from a Papa New Guinea atoll. Sydnie loves hiking, playing soccer, snow skiing, and spending time with family and friends. 

Welcome to UCLA, Sydnie!

New group member Jeana Drake

JLD lab photo

On August 17th my new group member Jeana Drake started. Jeana will work as a staff research associate to help me with the lab setup and to conduct our first field work off Los Angeles.

Jeana has a marine background and just finished her PhD in Paul Falkowski’ lab at Rutgers University in New Jersey (Congrats!). Her past research has focused on nitrogen cycling in coastal benthic marine systems.  These include brackish lagoons, coral atolls and fringing reefs, and seagrass beds.  Most recently, she has used biochemical, geochemical, and molecular biology tools to describe the identity and function of proteins used by stony corals to make their skeletons.

Welcome, Jeana, to UCLA and my lab!

Ocean currents impact methane consumption

Study in Nature Geoscience on interactions between marine microbiology and oceanography

Offshore the Norwegian Svalbard archipelago, methane gas is seeping out of the seabed in several hundred meters depth. Luckily, bacteria are consuming a large proportion of the methane before it reaches the surface and is released to the atmosphere, where it acts as a greenhouse gas. An interdisciplinary study conducted by researchers at the University of Basel and the GEOMAR Helmholtz Centre for Ocean Research Kiel could now show that ocean currents can have a strong impact on methane removal. The renowned journal Nature Geoscience has published the study.

Joint press release of the University of Basel and the GEOMAR Helmholtz Centre for Ocean Research Kiel

Large amounts of methane – whether as free gas or as solid gas hydrates – can be found in the sea floor along the ocean shores. When the hydrates dissolve or when the gas finds pathways in the sea floor to ascend, the methane can be released into the water and rise to the surface. Once emitted into the atmosphere, it acts as a very potent greenhouse gas twenty times stronger than carbon dioxide. Fortunately, marine bacteria exist that consume part of the methane before it reaches the water surface. Geomicrobiologists and oceanographers from Switzerland, Germany, Great Britain and the U.S. were able to show in an interdisciplinary study that ocean currents can have a strong impact on this bacterial methane removal. The international scientific journal Nature Geoscience has published the study.
The data was collected during an expedition in the summer of 2012 aboard the research vessel MARIA S. MERIAN. At that time, the international research team was studying the methane seeps off the west coast of the Norwegian Svalbard archipelago. “Already then, we were able to see that the level of activity of the methane consuming bacteria changed drastically over very short time spans, while at the same time many oceanographic parameters such as water temperature and salinity also changed”, explains Lea Steinle, first-author of the study and PhD student at the University of Basel and the GEOMAR Helmholtz Centre for Ocean Research Kiel. For her PhD thesis, Steinle studies where and how much methane is consumed in the ocean water column by bacteria.

In order to test if the fluctuations measured during the four weeks of the expedition were only random observations or based on typical and recurring processes, oceanographers of the GEOMAR later took a closer look at the region with a high resolution ocean model. “We were able to see that the observed fluctuations of the oceanographic data and the activity level of the bacteria can be traced back to recurring shifts in the West Spitsbergen Current”, says Prof. Dr. Arne Biastoch from the GEOMAR. The West Spitsbergen Current is a relatively warm, salty current that carries water from the Norwegian Sea to the Arctic Ocean. “It mostly runs very close to the coast. Shifts in the current strength are responsible for the meandering of the current. Then, in a matter of a few days, the current moves miles away from the coast”, explains Professor Biastoch further.

If the current runs directly over the methane seeps near the coast or continues on the open sea, impacts the methane filtration. “We were able to show that strength and variability of ocean currents control the prevalence of methanotrophic bacteria”, says Lea Steinle, ”therefore, large bacteria populations cannot develop in a strong current, which consequently leads to less methane consumption.”

In order to verify if these results are only valid for Spitsbergen or are of global importance, the researchers studied in a second, global ocean model how ocean currents are varying in other regions of the world with methane seeps. “We saw that strong and fluctuating currents are often found above methane seeps”, says Dr. Helge Niemann, biogeochemist at the University of Basel and one of the initiator of the study. His colleague Prof. Dr. Tina Treude, geomicrobiologist at the University of California Los Angeles adds: “This clearly shows that one-time or short-term measurements often only give us a snapshot of the whole situation.” In the future, fluctuations of bacterial methane consumption caused by oceanographic parameters will have to be considered, both during field measurements as well as models.

Reference:
Steinle, L., C. A. Graves, T. Treude, B. Ferré, A. Biastoch, I. Bussmann, C. Berndt, S. Krastel, R. H. James, E. Behrens, C. W. Böning, J. Greinert, C.-J. Sapart, M. Scheinert, S. Sommer, M. F. Lehmann, H. Niemann (2015): Water column methanotrophy controlled by a rapid oceanographic switch. Nature Geoscience, http://dx.doi.org/10.1038/ngeo2420